Photoresist compositions comprising a water-soluble polymeric material and a crosslinking agent therefore are well-known in the art. The use of such compositions as a negative photoresist in negative photoetching is likewise well-known. Photoetching utilizing a negative photoresist, in essence, comprises applying an aqueous photoresist composition to the substrate to be etched and selectively exposing the photoresist to light thereby causing certain portions to become insoluble upon development. The soluble portions of the photoresist are then removed and the exposed substrate etched to produce the desired pattern.
It is known that, in negative photoresists such as discussed above, the water-soluble polymeric material, e.g., polyvinylpyrrolidone, poly(vinyl alcohol), polyacrylamide and the like, is cross-linked by the photosensitive crosslinking agent upon exposure to light. Cross-linking of the polymeric material renders it insoluble in the developer solvent. Since crosslinking has taken place selectively by exposure of only selected portions of the photoresist to light through a conventional mask, removal of the remaining soluble photoresist forms the desired image. The substrate upon which the photoresist is formed is then etched to produce the desired pattern.
The use of certain bisazide compounds as photosensitive cross-linking agents in water-soluble polymeric materials such as polyvinylpyrrolidone is likewise known. The conventional use of such compounds is well documented in the patent literature. For example, U.S. Pat. No. 3,917,794 discloses water-soluble bisazide compounds such as 4,4'-diazidobenzalacetophenone-2,2'-disulfonate, 4,4'-diazidostilbene-2,2'-disulfonate and 4,4'-diazidostilbene-.gamma.-carboxylic acid as suitable crosslinking agents with water-soluble polymeric materials in a particular process for forming a pattern of photoresist on a surface. U.S. Pat. No. 4,099,973 discloses the addition of certain alcohols to compositions containing water-soluble polymeric materials and such conventional bisazide crosslinking agents. Conventional bisazide crosslinking agents such as discussed above are disadvantageous in that they have a tendency to explode under certain circumstances.
While the use of bisazide compounds such as 4,4'-diazidostilbene-2,2'-disulfonic acid as crosslinking agents for aqueous photoresist compositions is well-known to those skilled in the art, heretofore, the corresponding amino and/or nitro compounds have not been suggested for such use.